Biliary protein output by isolated perfused rat livers. Effects of bile salts

Abstract

The output of proteins into bile was studied by using isolated perfused rat livers. Replacement of rat blood with defined perfusion media deprived the liver of rat serum proteins (albumin, immunoglobulin A) and resulted in a rapid decline in the amounts of these proteins in bile. When bovine serum albumin was incorporated into the perfusion medium it appeared in bile within 20 min and the amount in the bile was determined by the concentration of the protein in the perfusion medium. The use of a defined perfusion medium also deprived the livers of bile salts and the amounts of these, and of plasma-membrane enzymes [5'-nucleotidase (EC 3.1.3.5) and phosphodiesterase I], in bile declined rapidly. Introduction of micelle-forming bile salts (taurocholate or glycodeoxycholate) to the perfusion medium 80 min after liver isolation markedly increased the output of plasma-membrane enzymes but had no effect on the other proteins. The magnitude of this response was dependent on the bile salt used and its concentration in bile; there was little effect on plasma-membrane enzyme output until the critical micellar concentration of the bile salt had been exceeded in the bile. A bile salt analogue, taurodehydrocholate, which does not form micelles, did not produce the enhanced output of plasma-membrane enzymes. This work supports the view that the output of plasma-membrane enzymes in bile is a consequence of bile salt output and also provides evidence for mechanisms by which serum proteins enter the bile.

Tubulovesicular transport of horseradish peroxidase in isolated rat hepatocyte couplets: Effects of low temperature, cytochalasin B and bile acids

“…When TCA generates choleresis, biliary secretion of lipids -especially cholesterol and phospholipids -is also enhanced and is linearly proportional to bile acid secretion to bile (25,26). This is accompanied by increased biliary secretion of canalicular membranous enzymes, including alkaline phosphatase and leucine aminopeptidase (27,28).…”

Identification of B10, an alkaline phosphodiesterase of the apical plasma membrane of hepatocytes and biliary cells, in rat serum: Increased levels following bile duct ligation and during the development of cholangiocarcinoma

“…In bile, one form has the same apparent molecular mass as that of the form found in the membrane and may be the result of solubilization by the detergent action of bile salts, as suggested for other canalicular membrane proteins found in bile. [27][28][29] The other form of B10 in bile has a smaller molecular mass than the form present in serum. Shedding 30 can cause the release of membrane proteins from plasma membranes; however, removing membrane fragments from cells would generate circulating forms with the same apparent molecular mass as did the membranous form on sodium dodecyl sulfate-polyacrylamide gel electrophoresis.…”

Effect of diosgenin on biliary cholesterol transport in the rat

“…Bile was collected immediately. After 20 min the liver was isolated in situ and perfused with a recirculating medium consisting of supplemented Krebs-Ringer bicarbonate buffer (Barnwell et al, 1983b) containing 30 % (v/v) sheep erythrocytes. Bile was collected from perfused livers for 2 h in 30 min portions and stored at -20°C pending analysis of lipids (cholesterol, bile salts and phospholipid).…”